A fuel injector is described in German Patent Application No. DE 195 34 445. The fuel injector for internal combustion engines described therein includes a nozzle needle, which is axially movable in a nozzle body and can be actuated by a piezoelectric actuator and which is held in a closing position by a compression spring. The fuel is supplied by an external source at a freely adjustable pressure. The nozzle needle has a central bore, and the actuator, which concentrically surrounds the nozzle needle, is sealed from the fuel pressure by a sealing surface.
A particular disadvantage of the fuel injector described in German Patent Application DE 195 34 445 is that, due to the influence of the fuel pressure, the lift of the piezoactuator can vary by up to 30% of the nominal lift, the sealing surfaces notwithstanding.
Furthermore, it is disadvantageous that, due to the length of the valve needle, oscillations are induced therein, which can lead to uncontrollable bouncing.